Air heater for furnaces



Patented June 27, 1922.

2 SHEETS-SHEET I.

' W. F. KEENAN, JR.

AIR HEATER FOR FURNACES.

APPLICATION FILED JULY 24,1920. I

Patented June27, 1922.

2 SHEETS-SHEET 2.

UNITED STATES.

PATEN OFFICE.

WALTER mamas KEENAN, an, on NEW YORK, N. Y., ASSIGNOR 'ro POWER srncmmyCOMPANY, OF NEW YORK, N. Y.,

A CORPORATION OF NEW YORK.

AIR HEATER FOR FURNACES.

-Application filed July 24, 1920. Serial No. 398,680.

To all 'whom it may concern Be it known that I, WALTER F. KEENAN,

' Jr., a citizen of the United States, residing at New York, in thecounty and State of New York, have invented certain new and usefulImprovements in Air Heaters for Furnaces, of which the following isafull, clear, and exact description.

In certain arts it is necessary to produce and supply highly heated airin very considerable volume and at substantially unlform temperature,but the means heretofore used for this purpose have proved inadequateand uneconomical. The prlmary object of my present invention is toprovide a better means for raising the air .in the required volume andat the proper pressure, to the desired temperature, and it consists,broadly, in such disposition of the air conveying tubes or channels thatwhile having the proper length to phermlt of the maximum absorption ofheat, t approximately the same heatlng effect whereby the averagetemperature of the issuing air will be the same from all of them.

In explanation of this, let us assume a series or bank of tubes throughwhich air to be heated is passed and that such bank of tubes is arrangedin a passage for hot gases from a suitable furnace. It is manifest thatwithout special provision to the contrary, those tubes which are nearestthe source of heat will deliver hotter air than those which are moreremote therefrom, and this is undesirable.

To avoid this objection I so arrange the tubes that each shall passthrough the heating current of gas at two points, of such temperaturethat their average shall always be the same. From this it results thatthe total or aggregate amount of heat absorbed by such tubes as a wholewill be the same.

This invention may be carried out in va-' to the heat absorbing tubes.

ey will be exposed to .approximately the same.

suitable form of furnace 1 burning solid fuel, gas or oil and comprisinga fire or flame chamber 2, and an upper lateral chamber 3 to preventdirect access of the flames The air tubes are designated by the numeral4; each tube is approximately U- shape, its legs crossing the passage 3at two points. The cold air is introduced into an inlet box or header 5with which one end of each tube is connected and taken off from the boxor header 6, with which the opposite ends of all the tubes connect. Thecentral horizontal portions of the tubes preferably extend across aheat-resisting wall or partition 7.

Those portions of the tubes 4 which are immedlately exposed to the heatare enclosed in a casing composed of cast-iron rings 8 which increasethe heat-absorbing surface and serve as a protection to the tubes roper.All of the tubes, it will be observed, are in multiple, whereby apassage of large area for.the air is afforded and the pressure requiredfor forcing the air through greatly reduced.

The tubes which have one leg in that portion of the passage nearest thefire, and where the temperature is highest, have their other legs inthat portion most remote from the fire or where the temperature islowest. The next and the succeeding rows of tubes are similarlyarranged, so that the average heating effect upon all of the tubes willbe The inner or shortest tubes, for example, pass through the passage 3at two points of nearly the same temperature, but which will average upthe same as the two points nearest and most remote from the source ofheat.

The hot gases after sweeping the bank of tubes and imparting their heatthereto, pass oil by a flue 9 which may be provided with an inspectiondoor 10 and a draft-regulating damper 11.

The specific construction of the furnace, except in the respects abovenoted, is largely immaterial. This also applies to the materialsemployed in its construction, but in any case the principle ofconstruction hereinabove set forth should be carefully observed. If, forexample, all of the tubes 4 were of the same dimensions and connectedcorresponding points in the two boxes or headers, it is manifest thatthe only way to prevent excessively uneven heating of the air thereinwould be to create by some appropriate means a whirling or eddying ofthe air in the boxes.

lVhat I claim as my invention is 1. An air heater comprising a passagefor the hot gases, a bank of U-tubes for the air to be heated with theirparallel legs crossing said passage and so disposed that each tube ofthe bank will be exposed to the same aggregate effect of the hot gasesas any of the other tubes.

2. An air heater comprising a bank of tubes arranged in a passage forhot gases,

each tube of the bank crossing said passage at two points, thetemperatures at which average the same as the average at the points ofcrossing of any other tube.

3. An air heater comprising a bank of U-tubes connected in multiple withinlet and outlet headers, and crossing a passage for hot gases, eachtube having one leg near the source of heat and the other remotetherefrom, so that the temperatures at the two points of crossing willaverage the same. 4:. An air heater having a passage for the hot gases,a bank of U-tubes, the parallel legs of which cross said passage at twopoints, means outside-the assage for supplying to the legs more remotefrom the furnace air to be heated and similar means for receiving theheated air from the other legs, the said tubes being of diiferentlengths and so connected to the said means that each is exposed to thesame aggregate heating effect and delivers air heated to the sametemperature;

In testimony whereof I hereto aflix my signature. I

. WALTER FRANCIS KEENAN, Jr.

